Optimized distortion correction technique for echo planar imaging

Nan Kuei Chen, Alice M. Wyrwicz

Research output: Contribution to journalArticlepeer-review

74 Scopus citations


A new phase-shifted EPI pulse sequence is described that encodes EPI phase errors due to all off-resonance factors, including Bo field inhomogeneity, eddy current effects, and gradient waveform imperfections. Combined with the previously proposed multichannel modulation postprocessing algorithm (Chen and Wyrwicz, MRM 1999;41:1206-1213), the encoded phase error information can be used to effectively remove geometric distortions in subsequent EPI scans. The proposed EPI distortion correction technique has been shown to be effective in removing distortions due to gradient waveform imperfections and phase gradient-induced eddy current effects. In addition, this new method retains advantages of the earlier method, such as simultaneous correction of different off-resonance factors without use of a complicated phase unwrapping procedure. The effectiveness of this technique is illustrated with EPI studies on phantoms and animal subjects. Implementation to different versions of EPI sequences is also described.

Original languageEnglish (US)
Pages (from-to)525-528
Number of pages4
JournalMagnetic Resonance in Medicine
Issue number3
StatePublished - 2001
Externally publishedYes


  • Echo planar imaging (EPI)
  • Field mapping
  • Geometrical distortions
  • Multichannel modulation

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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